Well, Naruto for sure. His friends from Team 7 are highly likely to be in it. But also, characters like Tsunade. As the Hokage and a great medical ninja, she could be consulted if Naruto's illness is really serious. Jiraiya might also make an appearance in Naruto's sick day fanfiction, perhaps reminiscing about his own times when he was sick as a young ninja.
In many Naruto Shippuden fanfictions where Naruto gets sick, it often shows a different side of his character. Usually, his friends like Sakura and Kakashi would be very worried. Sakura might use her medical skills to take care of him. And his enemies might take this opportunity to try and attack. But Naruto's strong will would still be there even when he's sick. He might not be able to fight as powerfully, but his determination to protect the village would remain unshaken. This kind of fanfiction can explore the relationships in the Naruto universe more deeply when the main character is in a vulnerable state.
Well, in many fanfictions, characters like Sakura might immediately take on a more nurturing role. She could be seen gathering medical supplies and constantly checking on Naruto's condition. Kakashi, on the other hand, might show his concern in a more understated way. He could be by Naruto's side, offering quiet words of encouragement or just being there as a reassuring presence. Sasuke might initially seem aloof but could end up showing his care in his own unique way, perhaps by secretly training extra hard to protect the village while Naruto is sick.
One common plotline is that Naruto's friends take care of him. For example, Sakura might use her medical skills to nurse him back to health. Another could be Naruto having flashbacks or deep thoughts while sick, perhaps about his lonely childhood. And sometimes, enemies might take advantage of his weakened state, leading to some tense situations where his friends have to protect him.
Another theme is the struggle against the illness itself. The fanfiction might detail how Naruto battles the sickness, both physically and mentally. He could be in a lot of pain but still tries to keep his positive attitude.
In this kind of fanfiction, Kakashi would probably make sure Naruto is comfortable first. He might tuck Naruto into bed, just like how a caring mentor would do. Then, he'd likely prepare some warm soup for Naruto to help him get better.
His teammates, Sasuke and Sakura, would surely be involved. Sasuke, although he may not show it as much, still cares about Naruto. He would keep an eye on Naruto's condition, and if there was any sign of danger, he would be ready to protect him. Sakura would be more hands - on with the medical care, checking his temperature, giving him medicine, and making sure he rests properly.
Well, in the fanfiction, perhaps Naruto realizes that Konoha's politics are too complex. There are always hidden agendas and power plays. He, being a straightforward person, might get tired of all the behind - the - scenes stuff. Also, he may feel that his friends are changing because of Konoha's influence. For example, they might be more focused on the village's reputation rather than their true feelings, which makes Naruto sick of it all.
In fanfiction, Naruto could feel sick due to overusing his chakra. He often pushes himself to the limit in battles and training, and this excessive chakra use might take a toll on his body, making him feel ill.
One common element is the concern of the people around Naruto. Since he is just a baby and sick, characters like the Third Hokage might be more protective. Another element could be the mystery behind his sickness. Maybe it's not just an ordinary illness but something related to his jinchuriki status.